Postal and delivery services were used in the 2001 bioterrorist attacks as a conduit to disperse and release anthrax across the United States. Letters containing a dried form of Bacillus anthracis spores were mailed through the U.S. Postal Service to several news media offices and two Democratic U.S. Senators. Several postal agents were directly in contact with the anthrax spores when handling the closed mail pieces. When the letters were opened, the volatile powder was dispersed and the spores inhaled. In the following months, five people died from anthrax spores inhalation and a total of eighteen others contracted some form of the disease. This event caused a panic wave in the population: several hundred thousands of people took broad-spectrum antibiotics, and even more purchased antibiotics for prophylaxis.
As bad as the anthrax attacks were, an outbreak of a biologically engineered pathogen dispersed by the mailing system would have been potentially more devastating. According to some biodefense specialists, the “senate” anthrax can be considered as a perfect example of a “bioweaponized” agent, as highly pure dried spores were successfully converted into an advanced aerosol. The processes of production of a bioweapon are technically complex. Inhalable microparticles have to be of a specific size range, typically one to five micrometers: particles smaller than one micrometer behave as a gas and are inhaled and exhaled from the respiratory system whereas particles of more than five micrometers are too large to stay airborne for a long time. Untreated anthrax spores, which are few micrometers in size, when introduced into an envelope and being subjected to mechanical contact with one another, tend to clump in large clusters due to adhesive properties of their surface. A specific treatment (aerosolization, weaponization) is performed to keep them dispersed and ensure that they have a proper size to be airborne for a long time.
Nowadays, suspicious mail pieces are neutralized by means of various types of irradiation or chemical procedures. U.S. Pat. No. 6,660,227 relates, for example, to a device in which mail pieces are isolated, analyzed and further exposed to ultraviolet irradiation. Among the main problems of such systems is that UV irradiation can only be used for sterilizing the external side of the mail pieces, as light emitted in this region of the spectrum does not penetrate the paper. U.S. Pat. No. 6,737,029 relates to a system for sterilizing mail articles by introducing them into a confined chamber which is filled with ozone to a degree that guarantees ozonization of all organic compounds, including viral nucleic acids and bacteria. Although this system is efficient for sterilizing the interior of the mail piece, the process is slow and expensive, energy consuming, and requires specifically trained staff to operate. Moreover, treatment of residual ozone used during sterilization is critical as small amounts of this gas are carcinogenic for humans.
Sterilization of all the circulating mail to eliminate the risk of a terrorist attack seems to be unachievable as it would be time-consuming, energy-consuming, and highly expensive. Therefore, modern strategies tend to direct their effort to thwart the volatility of the harmful microsized agents. WO 03/057260 relates, for example, to a method for reducing “volitation” of airborne biological agents while processing mail, using an apparatus that confers a charge to the microparticles in a special pre-charging chamber. Once charged, the particles which are located out of envelopes are attracted by an electric field by means of coulombic forces and are precipitated onto a surface having an opposite charge. The mails are then further processed for analysis and sterilization. This method and the described apparatus are well known in the field of air cleaning as electrostatic precipitator (ESP). However, for use in reducing powder volatility, ESP has several disadvantages:                efficiency of ESP is high only under special conditions—geometry of DC field and undisturbed air flow—which definitely cannot be met for the transporter carrying envelopes and other mailed objects of arbitrary positions and dimensions. Correspondingly, this method can not fulfill its main goal—to eliminate volatility of dangerous particles which came out of their envelopes due to their imperfect isolation.        said charging induces a repulsive effect between the particles, and also between the particles and envelopes, effectively increasing the volatility of non-captured particles.        method is time consuming because a lengthy time exposure is required to ensure that all the particles are charged;        electric field has to be constantly maintained throughout the mail transportation to the sterilization chamber in order to avoid particles spreading;        
There is therefore a need for a method and an apparatus capable of neutralizing potentially harmful powders enclosed in mails, which overcome the disadvantages of the prior art.
It is therefore an object of the present invention to provide a fast and effective method for neutralizing harmful powders in mail by reducing the volatility of microparticles.
It is another object of the present invention to provide a method for the detection and characterization of harmful powders in mails.
It is a further object of the present invention to provide a method for the deactivation of harmful powders in mails.
It is yet a further object of the present invention to provide an apparatus for the neutralization of harmful powders in mails, and optionally their identification and deactivation.
Other objects and advantages of the present invention will appear as the description proceeds.